Errata

The "demonstrations/examples" don't work.

------My Result 1 -------
In [1]: !!ls apa*py
ls: cannot access apa*py: No such file or directory
Out[1]: SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
0:

In [2]:
------- End My Result 1 ----------

The second example doesn't work either
------My Result 2 -------
In [2]: !!ls e*py
ls: cannot access e*py: No such file or directory
Out[2]: SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
0:
------- End My Result 2 --------

The third example doesn't work either
-------- My Result 3 --------
In [3]: !!ls t*py
ls: cannot access t*py: No such file or directory
Out[3]: SList (.p, .n, .l, .s, .grep(), .fields() available). Value:
0:

---------
---------
Python 2.5.2 (r252:60911, Sep 30 2008, 15:42:03)
IPython 0.8.4

from diskwalk_api import diskwalk
In [2]: files = diskwalk("/tmp")
In [3]: from fnmatch import fnmatch
In [4]: for file in files:
...: if fnmatch(file,"*.txt"):
...: print file


should be files = diskwalk("/tmp").enumeratePaths(), diskwalk is not an iterable object

On page 189, Example 6-8

missing from os.path import getsize
in ipython session before invoking getsize

Example 10-9 does not use the args.pop construct as cited in the text:

"Due to the power of python and *args, we can arbitrarily run commands using our function as a factory. Each command gets popped off a list starting at the beginning due to the args.pop(0) syntax."

but is instead a duplication of the subsequent example using the for loop construct.

The example code contains an incorrect sequence of calls.
The curses.wrapper call instantiates a screen, thus the curses.initscr call in __init__ is unnecessary. Due to these problems the screen is not reset on exiting the application.

A way the problem gets solved is as follows: (note this is a file_viewer instead of a log_viewer)


#!/usr/local/bin/python3.0
'file_viewer.py - uses curses to scroll thru a file'

import curses
import sys

class Viewer(object):

def page_up(self):
self.curr_topline = self.curr_topline - (2 * curses.LINES)
if self.curr_topline < 0:
self.curr_topline = 0
self.draw_lines()

def page_down(self):
self.draw_lines()

def load_lines(self):
fd = open(self.file, 'rb')
for line_no, line in enumerate(fd):
self.lines.append(str(line_no) + str(line))
fd.close()
self.draw_lines()

def draw_lines(self):
self.screen.clear()
for y in range(curses.LINES):
try:
line = self.lines[self.curr_topline]
except IndexError:
break
self.screen.addstr(y, 0, str(line) )
self.curr_topline += 1
self.screen.refresh()

def main_loop(self, stdscr, file=None):
self.screen = stdscr # as initialised by curses.wrapper
self.curr_topline = 0
self.file = file
self.lines = []
self.load_lines()
while True:
c = self.screen.getch()
try:
c = chr(c)
except ValeError:
continue
if c == 'd':
self.page_down()
elif c == 'u':
self.page_up()
elif c == 'q':
break

if __name__ == "__main__":
file = sys.argv[1]
curses.wrapper(Viewer().main_loop, file)

The sample code also contains:
- redundant screen.clear calls
- redundant initialisation of self.loglines

This example completely ignores the advice given by the authors in the tip just above of not relying on the location of elements within a configuration file. The example uses an absolute fixed location to populate the variable phrase.

The examples should follow the best practice identified by the authors not just a quick and easy implementation.